GD32F403xx User Manual
185
PA15 : JTDI
PA14 : JTCK/SWCLK
PA13 : JTMS/SWDIO
PB4 : NJTRST
PB3 : JTDO
By default, 5-pin standard JTAG debug mode is chosen after reset. Users can also use JTAG
function without NJTRST pin, then the PB4 can be used to other GPIO functions. (NJTRST
tied to 1 by hardware). If switch to SW debug mode, the PA15/PB4/PB3 are released to other
GPIO functions. If JTAG and SW not used, all 5-pin can be released to other GPIO functions.
Please ref er to
General-purpose and alternate-function I/Os (GPIO and AFIO) .
11.2.3.
JTAG daisy chained structure
The Cortex-M4 JTAG TAP is connected to a Boundary-Scan (BSD) JTAG TAP. The BSD JTAG
IR is 5-bit width, while the Cortec-M4 JTAG IR is 4-bit width. So when JTAG in IR shift step,
it first shift 5-bit BYPASS instruction (5’b 11111) for BSD JTAG, and then shift normal 4-bit
instruction for Cortext-M4 JTAG. Because of the data shift under BSD JTAG BYPASS mode,
adding 1 extra bit to the data chain is needed.
The BSD JTAG IDCODE is 0x790007A3.
11.2.4.
Debug reset
The JTAG-DP and SW-DP register are in the power on reset domain. The System reset
initializes the majority of the Cortex-M4, excluding NVIC and debug logic, (FPB, DWT, and
ITM). The NJTRST reset can reset JTAG TAP controller only. So, it can perform debug feature
under system reset. Such as, halt-after-reset, which is the debugger sets halt under system
reset, and the core halts immediately after the system reset is released.
11.2.5.
JEDEC-106 ID code
The Cortex-M4 integrates JEDEC-106 ID code, which is located in ROM table and mapped
on the address of 0xE00FF000_0xE00FFFFF.
11.3.
Debug hold function description
11.3.1.
Debug support for power saving mode
When STB_HOLD bit in DBG control register 0 (DBG_CTL0) is set and entering the standby
mode, the clock of AHB bus and system clock are provided by CK_IRC8M, and the debugger
can debug in standby mode. When exit the standby mode, a system reset generated.
When DSLP_HOLD bit in DBG control register 0 (DBG_CTL0) is set and entering the Deep-
sleep mode, the clock of AHB bus and system clock are provided by CK_IRC8M, and the
debugger can debug in Deep-sleep mode.
Содержание GD32F403 Series
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